Generally, a liquid detergent composition containing a surfactant, particularly a nonionic surfactant, is desirably blended with an alkali and a calcium-sequestering agent to improve washing effect. However, such surfactant is poor in compatibility with an aqueous solution containing an electrolytic salt at high concentration such as in concentrated alkali water, and is hardly stably blended.
In recent years, techniques solving this problem by emulsifying a nonionic surfactant, at a high concentration of an electrolyte, in the presence of an emulsifier such as a water-soluble polymer have been reported (JP-A 6-80998).
Usually, the emulsion is produced by a process wherein a mixture separated into an oily phase and an aqueous phase is emulsified with an emulsifying machine in a batch system such as a homo mixer or with an emulsifier in a continuous system such as a line mixer, or an oily phase is added to an aqueous phase forming a continuous phase and then emulsified with the same emulsifying machine.
On the other hand, the maintenance of the emulsifying machine in the continuous system arranged in a piping outside of a bath is improved as compared with the batch system, but there is a problem in burden (e.g. abrasion) on facilities and in productivity.
To solve these problems, JP-A 6-80998 supra describes an emulsifying method wherein a dispersion having an emulsifying polymer and a nonionic surfactant mixed in water is added under sufficient stirring at a relatively low rate of about 400 rpm with a propeller stirrer, and then a water-soluble inorganic salt is added to, and mixed with, the dispersion while stirring.